The present invention concerns a method and system for data communication with a microprocessor while the microprocessor is in a low-power or "sleep" mode. More specifically, the invention relates to an engine control module for an internal combustion engine that has a sleep mode when the engine is turned off.
In recent years, the control of internal combustion engines has branched away from the traditional mechanical linkage and analog approaches to an electronics or microprocessor based system of controls. In a typical vehicle, the operation of the engine is controlled by an engine control module (ECM) which receives a variety of input signals and output signals monitoring and controlling various components of the engine. For example, the ECM can send signals to a fuel system for controlling the amount of air and/or fuel sent to the engine cylinders. In addition to sending control signals, the ECM also receives signals from various sensors at the engine and drive train. For example, the sensors carry signals indicative of engine speed, fuel and air flow, intake and exhaust pressure, engine temperature, and the like. The ECM uses data related to the signals to calculate various engine operating parameters based upon algorithms contained within the ECM.
In addition, the ECM retains data in memory showing a complete history of the engine performance and operating parameters. For example, the ECM calculates and stores data for engine torque, horsepower, load factors, fuel consumption, duty cycles, cylinder firing times and the like. This information is stored in the ECM to be downloaded at predetermined intervals in the engine life. The downloaded information can be analyzed at a site away from the vehicle to evaluate the engine performance and make recommendations for servicing of the engine.
In contrast to the prior mechanical linkage and analog systems of the past, the electronic controllers and ECMs of the modern engine must be continuously connected to an electrical power source, such as the vehicle battery. Like most microprocessors, the typical engine control module maintains an internal clock, for example, that can maintain date and time of day information. This internal clock operates whether or not the engine and vehicle are being operated. Thus, the ECM usually requires its own hardwired power supply. In addition, the ECM and associated electronic components have generally high input power requirements. While the vehicle is operating, the alternator can easily provide for the power requirements of the ECM and associated components. However, these power requirements reduce fuel economy in proportion to the amount of engine output power that goes into driving the vehicle alternator. At the other end of the spectrum, when the vehicle is not operating, the ECM must draw its power from a storage battery.
In either circumstance, whether the vehicle is operating or idle, it is prudent and usually necessary to conserve the amount of electrical energy consumed by the ECM and its associated components. Consequently, the modern ECM, like the typical personal computer or microprocessor, has a "sleep" mode in which the ECM operates on reduced power. For example, the sleep mode of an ECM can terminate power to all elements of an ECM other than the real time clock. In another example, passenger vehicles that utilize automatic door lock transmitters must power the door lock receivers in the sleep mode to receive a door unlock signal from a transmitter. Since the energy requirements of components of this type are minimal, a vehicle can be maintained in a sleep mode for quite awhile on a typical vehicle storage battery without draining the battery. Similarly, when the engine is operating and the vehicle is on the road, certain portions or functions of the ECM can be directed to the sleep mode to conserve electrical power usage in real operating time. In that instance, software within the ECM determines what essential elements retain electrical power and which elements are disabled to reduce power consumption.
In a typical vehicle, the ECM is placed into the sleep mode when the key switch is turned to the "off" position. In many such systems, the ECM downloads data from volatile memory into non-volatile or flash memory immediately before entering the sleep mode. In these systems, the ECM exits the sleep mode, or returns to normal powered operation, when the key switch is turned to the "on" position, such as when the operator is starting the vehicle engine, or to the "auxiliary" position in which electrical power is provided without starting the engine. Software within the ECM runs through a power up protocol to enable the previously disabled components and initiate normal operation of the ECM. Since solid state electronics are utilized in these ECMs, the entry into and exit from the sleep mode happens in a matter of seconds.
One drawback with the sleep mode of any processor is that it is deaf to any communication other than certain external signals used to force the ECM out of the sleep mode. For example, some passenger vehicles with remote keyless entry transmit a signal to a vehicle sensor that sends a wake up signal to the ECM. In vehicles of this type, the keyless entry signal from the hand held transmitter turns on the ECM and causes it to unlock the doors, turn on the interior lights and begin the initial steps of a start up protocol. Beyond this capability, existing vehicle ECMs have no ability to transmit and receive information concerning engine operation and performance.
This detriment is most prominent in the use of heavy duty vehicles and equipment. In one example, a land mining site utilizes several heavy duty loading vehicles and hauling trucks to convey mined material from the mine site. In this arena, several vehicles are used to provide a continuous flow of material away from the mine site to a construction site, for example. As the hauling vehicles return, they queue up in a ready line at the mine site to await a new load of mined material. In order to preserve fuel and prevent engine overheating, the hauling vehicles are shut down at the ready line until the next load of material is available.
However, in this situation, the continuous activity of the engines requires that they be frequently monitored to discover and address developing problems in engine performance. Thus, the mine site operator will typically take readings of data from the ECM for evaluation while the vehicle is sitting in the ready line. In this circumstance, the vehicle engine must be kept running until the data is extracted. Moreover, in some cases, after the data has been analyzed certain parameter changes in the ECM may be required, which would necessitate a further transmission of data to the ECM. If the engine is shut off, it enters the typical sleep mode in which data communication is not permitted. Thus, the mine site operator is faced with the choice of keeping the engine running with all of the risks inherent with that option, or shutting the engine off and thereby eliminating any chance of recovering performance data from the engine.